1. Field
Embodiments relate to a polishing head in a chemical mechanical polishing apparatus and a chemical mechanical polishing apparatus including the same. More particularly, embodiments relate to a polishing head in a chemical mechanical polishing apparatus, which can polish a substrate evenly, and a chemical mechanical polishing apparatus including the same.
2. Description of the Related Art
In general, a wafer is manufactured into a semiconductor device, e.g., a chip may be manufactured by repetitively performing photolithography, ionic diffusion, etching, chemical vapor deposition, metal vapor deposition, or the like processes. A wafer, after undergoing the foregoing processes, may be further processed to form metal wiring thereon, e.g., to form a fine pattern.
With recent high integration, the structure of the semiconductor device has become multi-layered. That is, as higher integration is applied to the semiconductor device, a multi-layered wiring structure, where metal wiring, an insulation film, intermediate wiring, etc. constitute a plurality of layers, is formed on the wafer. Accordingly, the surface of the wafer needs to be planarized.
This is because if a fine pattern layer is sequentially formed on a wafer having another uneven fine pattern, a gap between the wafer having the unevenness and the mask placed on the wafer to form the fine pattern is not uniform. Therefore, a desired fine pattern would be out of focus of a projection lens and, thus, not precisely formed. Accordingly, the unevenness on the wafer is planarized to improve the precision of the fine pattern, e.g., by polishing the surface of the wafer.
For example, a chemical mechanical polishing (CMP) apparatus capable of both chemically and mechanically polishing the wafer may be used. The mechanical polishing refers to polishing of the surface of the wafer using friction between a polishing pad and the surface of the wafer by applying a predetermined load to the wafer and rotating the wafer in the state that the wafer is placed on the rotating polishing pad. The chemical polishing refers to polishing of the surface of the wafer using a chemical polishing agent, i.e., slurry supplied between the polishing pad and the wafer.
A conventional CMP apparatus may include a polishing station, on which the polishing pad is installed, and a polishing head positioned above the polishing station and pressing a wafer toward the polishing pad. Further, the polishing head is provided with a retainer ring surrounding a membrane in order to prevent the wafer and the membrane for pressing the wafer from being separated during the processes.